192 



The Soil in Relation to Disease. 



[parti. 



The absolute mm-i'm/U-m, occurred in August with 5 volumes per 1,000, but there 

 was a previous period of depression in January and March, also with 5 volumes per 

 1,000. In both layers there was a rise in January. 



Both localities agreed in constantly showing a larger quantity of carbonic acid 

 in the lower than in the upper layer. For purposes of more exact comparison, 

 attention must be confined to the period during which both localities were subjected 

 to observation. When this is done it appears that the absolute quantities of carbonic 

 acid present in the second locality were, as a rule, less than those in the first, but 

 that the periods of relative depression and elevation in amount of carbonic acid 

 exhibited a general coincidence in both places. In the second locality not only were 

 the amounts of carbonic acid less, but the fluctuations in the quantities present at 

 different times were also less than in the first locality. This comes out very clearly 

 in the following statement : — 



The only point of interest which calls for special remark in regard to this comparison 

 is the demonstration which it affords of the occurrence of local variations in the amount 

 of carbonic acid present in the soil of localities in close proximity to one another, and 

 to all appearance extremely similar in their nature. The sites of observation were 

 not more than 50 yards apart, and were both situated at similar and corresponding 

 distances from the walls of one and the same building. The processes going on in the 

 soil in the two places must have differed materially, in degree at all events, if not in 

 Jiind ; and if such processes occurring in the soil have any influence on health, it is 

 obvious that people inhabiting one end of the building must have been exposed to 

 different hygienic conditions from those living at the other end. Such an observation 

 is of special interest in connection with the extremely marked, and frequently apparently 

 inexplicable, localisation in the distribution of cholera within narrow limits — even 

 within the limits of individual buildings. 



(c?) — Gomparison of the amount of Carbonic Acid present in the Soil with the 

 Temperature of the Soil at similar depths. — (Chart III.) 



On consulting the tables and charts it becomes at once clearly evident that 

 the amount of carbonic acid present in the soil at various times is not determined 

 by the mere coincident temperature of the soil. Maximum temperature coincides 

 with minimum amount of carbonic acid at one period, and with a very large amount 



